Prime cost in construction contracts
In general terms, the ‘prime cost’ is the sum of the direct cost of materials and labour associated with a production process. It is the direct cost of the inputs to a process that are necessary to create the output. If the prime cost can be lowered, the process may become more profitable.
In construction, the term ‘prime cost sum’ (PC sum) is an allowance for the supply of labour, plant and materials to be provided by a contractor or supplier that will be nominated by the client. The allowance is exclusive of any profit mark up or attendance (such as material handling, scaffolding and rubbish clearance etc) by the main contractor. See prime cost sum for more information.
Prime cost contracts (sometimes referred to as cost plus contracts or cost reimbursement contracts) are contracts in which the contractor is paid the prime cost (the actual cost of labour, plant and materials) and a fee for profit and overheads.
Prime cost contracts are used where an early or immediate start on site is required even though design information is not complete, for example for urgent alteration or repair work. See Prime cost contract for more information.
Adjustments may be permitted to prime costs during the period of a contract to allow for inflation (fluctuations).
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
A safe energy transition – ECA launches a new Charter
Practical policy actions to speed up low carbon adoption while maintaining installation safety and competency.
Frank Duffy: Researcher and Practitioner
Reflections on achievements and relevance to the wider research and practice communities.
The 2026 Compliance Landscape: Fire doors
Why 'Business as Usual' is a Liability.
Cutting construction carbon footprint by caring for soil
Is construction neglecting one of the planet’s most powerful carbon stores and one of our greatest natural climate allies.
ARCHITECTURE: How's it progressing?
Archiblogger posing questions of a historical and contextual nature.
The roofscape of Hampstead Garden Suburb
Residents, architects and roofers need to understand detailing.
Homes, landlords. tenants and the new housing standards
What will it all mean?
The Architectural Technology podcast: Where it's AT
Catch-up on the latest episodes.
Edmundson Apprentice of the Year award 2026
Entries now open for this Electrical Contractors' Association award.
Traditional blue-grey slate from one of the oldest and largest UK slate quarries down in Cornwall.
There are plenty of sources with the potential to be redeveloped.
Change of use legislation breaths new life into buildings
A run down on Class MA of the General Permitted Development Order.
Solar generation in the historic environment
Success requires understanding each site in detail.
Level 6 Design, Construction and Management BSc
CIOB launches first-ever degree programme to develop the next generation of construction leaders.
Open for business as of April, with its 2026 prospectus and new pipeline of housing schemes.
The operational value of workforce health
Keeping projects moving. Incorporating unplanned absence and the importance of health, in operations.






















Comments
Construction on this page has been spelt incorrectly! - well spotted, this has been fixed